Font Size: a A A

The Characteristics And Ecological Restoration Machanism Of Vegetation In The Ecotone Between The Bedrock Area And Loess Area At West Shanxi Province

Posted on:2006-07-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:L S DongFull Text:PDF
GTID:1100360155464409Subject:Ecology
Abstract/Summary:PDF Full Text Request
The hilly loess region of west Shanxi province is the east margin of the loess plateau in China, and the Luliang mountain is the edge of this region. Luliang mountain is a region of bedrock, and the main type of natural vegetation of this region was natural secondary forest. But the region between luliang mountain and the yellow river as thick loess landform was agricultural region, and the natural vegetation was steppe. There was an ecotone between the luliang mountain and the loess hill region of west Shanxi province. In this paper , the character and machanism of vegetation succession was discussed. The main contents and conclusions were as follows: 1 Definition of ecotone between bedrock region and loess hill area and its significance In this paper, the definition of "ecotone between bedrock region and loess hill area"was be expounded, and this word meaned that "the transitional zone between the natural secondary forest in the bedrock mountain and the agricultural region in the loess hill area"。As the west Shanxi province, this ecotone refer to the zone between luliang mountain and loess hill area.This ecotone could be divided into two parts, one was the edge of the loess hill area, and there was some relict natural tree and shrub community.The other was bedrock mountain area. 2 Advances of the vegetation restoration strategy in loess plateau The advances of the prospect and target of the vegetation restoration of loess plateau, and the strategy of the vegetation construction was anlysed in this text. About the prospect and the target of vegetation restoration,the conclusion was put foreward from the study advances of three parts: geograph,geology and the spatial characteristics of vegetation. Also the different viewpoint from different scientists were reviewed. The key issue about "whether the forest vegetation extensively existed in the loess plateau or not"was discussed. Several kind of the strategy of vegetation restoration in the loess plateau was analyzed, also the study advances of district of vegetation construction was expounded. The prospect of vegetation restoration of loess plateau was discussed. The question that whether it was fit for forest construction in the loess plateau, could not be simply answered "yes"or "no".The experience of vegetation in recent decades demonstrated that the viewpoint which thought that the forest landscape was not right during historical period ,but the viewpoint that only the shrub or grass could be used in the vegetation construction in the loess plateau was not correct too.What we should do was realized the reality, summing up the experience of vegetation construction, adjusting and improving the direction and countermeasure. 3 The characteristics of flora of seed plants in the ecotone The floristic feature of the ecotone between the bedrock area and loess hill area was analyzed in particular.There are 354 species of seed plants, which belong to 204 genera and 64 families. Based on the statistics and analysis of families, genera and species in the present flora, the floristic feature were summarize as follows: The number of generas of the distributional types including cosmopolitan, old world tropical, E. Asia, pantropic were more than 10. The number of other distributional types was little. Also the floristic feature was contrasted as other region. In the edge of the loess hill area, there are 134 species of seed plants, which belong to 93 genera and 42 families. Which the proportion of ecotone was 37.85%,45.59%,65.63%. the area of the bedrock natural forest region was the important region in the loess plateau. 4 The main vegetation types and its spatial characteristics. According to the general principle of China vegetation classification, the vegetation form in zhongyang was devided.The spatial character of vegetation in the bedrock region and loess area was analyzed.The numerical classification of vegetation was used in this text. The method of two-way indicator species analysis(TWINSPAN) was used to divided the vegetation of natural forest community in the bedrock area. The result shew that 32 quadrats could be divided into 13 groups. There were some natural forest communities in the edge of the loess plateau. Whether this community could be looked as the evidence that it was possibility that the natural forest exist in the loess hill area. 5 The dominant species and species diversity in the ecotone. The spatial characteristics of the dominant species and the species diversity in different communities was analyzed in the bedrock region and loess area.The dominant species of communities along the altitude have an obvious transformation.The species richness of woodplant along the altitude decreased gradually, the richness of tree species was high at high altitude, but the shrub species richness was high at the low altitude. The species diversity index of community in high altitude was also high.The cody and whittaker indices between two communities shows obvious regularity.The indices of the two neighboring communities was least, but when the distance was high, the two indices was also high.The Jacard and sorensenr indices of community similarity show inversely that the indices of the two neighboring communities was large. The different vegetation types had different species richness and Shannon species diversity indices. The indices of richness and Shannon diversity of natural shrub community were greater than plantation community, and the indices of shrub community in shady slope was greater than the community in the sunny slope.The natural forest community of Platycladus orientalis mainly located at sunny slope which was very dry, so its species richness and diversity indices were very low.In the end , more than 30 species including trees and shrubs were provided for different topography in the loess plateau area. 6 The succenssion regularity of natural vegetation in the ecotone. The succession phenomena and pioneer species in the bedrock region and loess area were studied in this text.At the same time , we studied the height and diameter structure and complexity of community in the natural secondary forest. The complexity from the height structure show that it was high at the ante-stage, and low at the step-stage as the succession of community proceeding. The statistical character of regeneration of forest community was studied. At the same time, the prospect of community succession was analyzed.The structure and species of regeneration was also analyzed, and this provided plant material for the vegetation construction in this region. 7 Ecological evaluation of plantation forest. The ecological evaluation of the two species of Pinus tabulaeformis and Robinia Pseudoacacia in the loess plateau were analyzed. The breast-high diameter and height of plantation at zhongyang was contrasted with other region of other part of loess plateau in china. The main problem of the two kinds plantations were analyzed in the plantation management.Thesuitable density table of Pinus tabulaeformis was draw up.This table was draw up in the common site quality. So when the site quality was high, the density of plantation should be low, but when the site quality was low, the density should be high too. 8 The biomass of the communities in the ecotone. The biomass of the mail vegetation types in the bedrock and loess area was analyzed, the difference among the vegetation types was also be studied. The result show that the high yield of biomass was possible in the good water condition in the loess area, for example the biomass of the plantation which was 37 age was 110t/hm2.The biomass of shrub with herb and litters with moss in the forest communities show a obvious regularity,the biomass of litter and moss in coniferous forest was high, as the37 age plantation could reach to 25t/hm2. But the biomass of shrub and herb was high in the broad-leaf forest. 9 The soil water content and nutrient contents in the process of vegetation restoration The precipitation resources in zhongyang was analyzed in recent ten years.The spatial character of soil content was analyzed in the bedrock and loess area.Through the soil water content in different vegetation types was contrasted in loess hill area.The soil nutrient content character of main vegetation types in the bedrock region and loess area. We contrasted the norm of nutrient content norm of main vegetation types between the bedrock region and loess area. The result show that total N, available N, organic matter norm in the bedrock was obviously greater than the norm in the loess area.The available K and available P content in two area was similarity, otherwise the available K in the loess area was little greater than bedrock area.the soil pH indices norm in the loess area was 8.45, but the soil pH indices norm in the bedrock area was 7.92.Whether The difference of the soil nutrient content between the bedrock and loess area had greater influence to the vegetation spatial character, was a key question which we should study in the future. 10 Anylysis of vegetation restoration strategies in the ecotone In this paper, we discussed the problem, counter measure and future prospect of vegetation restoration. The western area of shanxi loess plateau can be distinguished two parts by the geomorphic and vegetation features, one was earth-rocky forest zone mainly in the east of this region; the other was loess agricultural zone in the west by the yellow river. Earth-rocky forest zone should Close the hillsides to facilitate afforestation, This text bring forward "closing the hillsides to facilitate afforestation was the main instrumentality and the artificial promotion measures was assistant instrumentality"as the long-term management strategy of secondary forest region .otherwise the loess zone should prohibit pasture outside on hillside, or carry out rotation grazing. The level of the management and technique of artificial aforestation should be enhanced in time. For the target of reconstructing the vegetation of this area, we must change the extensive management of the economy. The policy of protection and closing the land should be attached enough importance to, we also should use more native trees than exotic trees. Only through these measures, the vegetation restoration and controlling the soil erosion may come true in the area of the western shanxi province.
Keywords/Search Tags:The western part of Shanxi province, Bedrock area, The loess hill area, Vegetational characteristics, Mechanism of vegetation restoration, The characteristics of flora, Community features.
PDF Full Text Request
Related items